To be honest, I would go to a more bunny-savvy vet. This vet doesn’t sound all that great if they’re saying they aren’t sure if a spay will fix hormonal behaviors or if they don’t think its necessary to spay a female.
Her hormones sound like they have decided to finally peep through, and yes spaying will fix this behavior. It won’t fix it right away, but within a month you should notice a positive behavior change. She might get worse before she gets better (known as a post-spay craze when hormones are all over the place). Overall it will help. In the mean time you can just continue with the foundation you’ve been setting all along.
A spay is essential for the health and well being of a female bunny, as unspayed females over the age of 3 years old have a high risk of reproductive cancers. These cancers make it necessary to perform an emergency spay, which can sometimes be fatal. So it’s absolutely needed.
Spays are always going to be more expensive than a neuter because the surgery is more invasive. My boys were neutered for $350 each. It depends on the vet you go to. ASPCA vets and vets in large cities tend to charge in the $200-$300 range. There are low cost spay programs available, but at least in my area, $300 is around the norm depending on the level of care they give. If it’s only the surgery and then sending you home with pain meds… look for cheaper. The $350 I paid for each boy included 36 hours worth of after care at the vet, a 2 week follow up, and any pain meds or antibiotics they needed, so it was well worth it.